This invention relates to an automatic differential transmission gear comprising a gear box with a reduction planetary gear and a collecting planetary gear, there being two input shafts to the gear box, one of which is connected to the reduction gear and the second of which is connected to the collecting planetary gear, an output shaft of the transmission gear and an input shaft of the transmission gear. The input shaft of the reduction planetary gear is connected firmly or alternatively by way of a hydrodynamic element with the input shaft of the transmission gear, and the input shaft of the collecting planetary gear can be connected to the input shaft of the transmission gear through a connecting element. This invention is an improvement upon that disclosed in coassigned U.S. Pat. No. 3,903,757 to Hau et al, of Sept. 9, 1975.
Known automatic transmission gears deleteriously affect the rate of consumption of fuel of mechanisms in which they are incorporated such as motor vehicles. There is a trend toward the provision of an automatic transmission gear which permits a reduction of fuel consumption in comparison with automobiles with a classical manually operated transmission gear. Such automatic transmission gear, however, leads to the further complication of automatic transmission gears, and thus makes it difficult to employ them in cheaper automobiles.